In railroad vehicles, an electric motor is mounted on a truck disposed under a vehicle body. A rotational force of this electric motor is transmitted to wheels via joints and gear devices, and thereby the railroad vehicle travels.
Generally, an electric motor includes a case, a tubular stator core accommodated in the case, a rotor core disposed on an inner peripheral side of the stator core, and a rotor shaft fixed to the rotor core. The rotor shaft is rotatably supported by a bearing part.
Incidentally, regular maintenance is required for the bearing part which supports the rotor shaft. In general, maintenance of the bearing part requires disassembly of the electric motor with an operation of pulling the rotor core out of the stator core. However, such an operation of pulling out the rotor core from the stator core causes a heavy burden of operation. Therefore, a non-disassembling bearing exchange structure in which maintenance of the bearing part can be performed without pulling out the rotor core from the stator core has been proposed.
However, in a conventional non-disassembling bearing exchange structure, when a mistake is made in operation procedure, a problem such as the rotor core falling out from the stator core may occur. Therefore, an operator has to perform sufficient confirmation work not to make a mistake in the operation procedure. Therefore, an electric motor has room for improvement in terms of facilitating a maintenance operation.